Relating to radar apparatus

ABSTRACT

A method of operating a radar apparatus is disclosed. The method comprises: (a) capturing a first chirp of data in the cycle which generates D data samples from each of N antennas and storing the data in a local storage memory; (b) processing the captured data using a Fourier Transform to generate a set of range bin data, one for each antenna, where each set comprises R range bins; (c) transferring in a sequence of bursts the range bin data for the chirp from the local storage memory to a remote burst access memory where the data is arranged in a grid pattern, the grid pattern comprising data filled rows containing two or more unique range bins of data for the chirp held in a continuous strip of the remote burst access memory, the data filled rows being separated vertically from adjacent data filled rows by multiple rows which do not contain any bursts of data associated with the chirp, (d) repeating the steps (a) and (b) for each subsequent chirp of data in the cycle, (e) repeating step (c) after the range bin data for each subsequent chirp has been stored in the local storage memory so as to transfer in a sequence of bursts the range bin data for each subsequent chirp of data from the local storage memory to the remote burst access memory where the data is arranged in the same grid pattern used for step (c) but offset vertically by one or more rows to fit within the rows in the column that have not been written with data for any previously processed chirp in the cycle, (f) transferring from the remote burst access memory into the local storage memory, in one or more bursts, at least one continuous vertical block of data from the remote block that has a length equal to the number of different range bins, (g) process the data transferred into the local storage memory using a Fourier Transform to generate a set of velocity data comprising a set of velocity bins where each velocity-bin is generated from the values of the corresponding range bin for every antenna of the array, and repeating steps (f) and (g) until all of the data in the remote burst access memory black of data has been processed by the second FFT.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a national stage of Great Britain Patent ApplicationNo. 1806593.8, filed 23 Apr. 2018, the disclosures of which areincorporated herein by reference in entirety.

BACKGROUND TO THE INVENTION

This invention relates to improvements in FMCW radar apparatus, inparticular for mounting to a vehicle such as a car or truck.

It is known to use radar in the measurement of distance. En oneapplication radiation in the microwave region of the spectrum is emittedfrom a source towards a target. The target will reflect some of thisradiation back towards a detector, which is sensitive to radiation inthe microwave region of the spectrum. A microcontroller may then be usedto make a comparison between the emitted signal and the measured,detected, signal from which the range of the target from thesource/detector can be estimated.

A radar apparatus mounted to a vehicle may be used to detect thepresence of objects around the vehicle, which may be used as part of avehicle autonomous or semi-autonomous system such as active cruisecontrol.

It is known to provide a frequency shift key scheme to determine therange/distance from the signals. Distance can be measured from the phasedifference that is seen in the returned signal when the emitted signalis modulated by a small step change in frequency. The accuracy of themeasurement is related to the frequency step size. Similarly, therelative velocity can be measured by looking at the change in phaseshift between closely spaced chirps

There has been a significant amount of development work in the field ofradar systems, and many types of radar transmission techniques areavailable. One technique that has proven suitable for automotiveapplications is known as Frequency Modulated Continuous Wave (FMCW)radar. In an FMCW radar, the frequency of a signal transmitted by anantenna array is ramped up or down over a range of frequencies defininga chirp. This can be produced relatively simply using voltage controlledoscillator (VCO). The data collected from each chirp will comprise a setof perhaps 1024 data samples for each antenna in the array. The antennaarray can be of any suitable size, such as 16 antenna radar array. Thesedata samples may then be processed using a discrete Fourier Transform todetermine values for a set of range bins for the chirp. These may thenbe processed together with range bin values for a series of chirps toproduce a final set of velocity bin data for the radar apparatus.

In a practical implementation, each chirp offers a set of rangemeasures. The output of a MT taken on the chirps is a set of complexrange bins, the frequency and phase of which indicates a precise range.As the range changes from one chirp to the next (due to relative motion)the phase (and ultimately frequency) changes between chirps.

By performing an Fourier Transform, such as a Fast Fourier Transform(FFT) across the consecutive chirps in a given range bin, it is possibleto extract frequency (i.e. the rate of change of phase with time), whichis related to relative velocity.

A typical FMCW radar apparatus includes a microcontroller that performsthe function of processing the data from the antenna, usually using aFast Fourier Transform (FFT) or sequence of FFTs. The microcontrollersinclude an amount of fast access memory typically integrated onto thesame chip as the processing unit—typically a programmable logiccontroller. This memory is referred to herein as a local storage memory.This local storage memory is physically close to the processor core ofthe programmable logic controller and therefore faster to read and writefrom. It is used for the short term storage of data that is beingprocessed during operation of the apparatus.

The system also includes an external memory, referred to herein as aremote burst access memory, which is located physically further from theprocessing unit outside of the main processing element chip and thusslower to read from and write to. This memory is usually provided as adedicated memory chip and communicates with the processing unit across amemory bus. The remote burst access memory also is typically constrainedso that data can efficiently be written or read out in bursts of a fixedline length. Truly random access (which is desirable for FFT operations)is very inefficient, and reduces performance compared with burst accessmemory.

The local storage memory is designed to be truly random access but theremote memory is designed to allow a series of bursts of memory, eachburst comprising a line of data of fixed length, to be transferred tothe local storage memory on a request made across the memory bus. Aburst may consist of a data line that is at least 2 bytes or more bytesof data in length. A sequence of bursts may be written into any numberof rows of memory, but typically it is fastest to write a sequence ofbursts that correspond to a block of contiguous rows in the memory.

A problem with prior art radar apparatus is that to achieve a goodresolution over a wide range of distances, a very large amount of datamust be captured and processed. This will often exceed the amount ofhigh speed local memory that is available to the processor, requiringdata to be transferred out to a remote memory during the signalprocessing and later transferred back in for more processing. Becausethis transfer is relatively slow, the overall speed of the radar ingenerating range data will be limited. Providing enough high speed localmemory to avoid having to do this is at the time of writing is not costeffective.

SUMMARY OF THE INVENTION

A feature of the present invention is to ameliorate the limitationspresent in prior art methods of processing radar data where a largevolume of data is being processed.

According to a first aspect the invention provides a method of operatinga radar apparatus of the kind comprising an antenna array of N antennas,a processing unit which receives data captured from the antenna arrayand includes an area of local storage memory and a larger area of remoteburst access memory, the method comprising for a single cycle of theradar comprising two or more chirps of transmitted radar frequencysignal:

(a) capturing a first chirp of data in the cycle which generates D datasamples from each of N antennas and storing the data in a local storagememory,(b) processing the captured data using a Fourier Transform to generate aset of range bin data, one for each antenna, where each set comprises Rrange bins,(c) transferring in a sequence of bursts the range bin data for thechirp from the local storage memory to a remote burst access memorywhere the data is arranged in a grid pattern, the grid patterncomprising data filled rows containing two or more unique range bins ofdata for the chirp held in a continuous strip of the remote burst accessmemory, the data filled rows being separated vertically from adjacentdata filled rows by multiple rows which do not contain any bursts ofdata associated with the chirp,(d) repeating the steps (a) and (b) for each subsequent chirp of data inthe cycle,(e) repeating step (c) after the range bin data for each subsequentchirp has been stored in the local storage memory so as to transfer in asequence of bursts the range bin data for each subsequent chirp of datafrom the local storage memory to the remote burst access memory wherethe data is arranged in the same grid pattern used for step (c) butoffset vertically by one or more rows to fit within the rows in thecolumn that have not been written with data for any previously processedchirp in the cycle,(f) transferring from the remote burst access memory into the localstorage memory, in one or more bursts, at least one continuous verticalblock of data from the remote block that has a length equal to thenumber of different range bins,(g) process the data transferred into the local storage memory using aFourier Transform to generate a set of velocity data comprising a set ofvelocity bins where each velocity-bin is generated from the values ofthe corresponding range bin for every antenna of the array, andrepeating steps (f) and (g) until all of the data in the remote burstaccess memory block of data has been processed by the second FFT.

The applicant has appreciated that by transferring data across from thefast local storage memory to the remote burst access memory in arepeating pattern of single data lines for each chirp prior to all ofthe Fourier Transforms for being taken for all the chirps in a cycle itis possible to use much less local storage memory compared to prior artarrangements that take an FFT for all the chirps before transferringdata.

By storing the data in the remote memory in blocks, with each blockcorresponding to one chirp, a fast transfer back to the local memory ispossible. The storage in blocks is achieved in a very efficient mannerby processing one chirp at a time in the local storage memory andwriting out to spaced locations in the remote memory to form a grid, andthen repeating to interleave the data.

The method in step (f) may transfer all of the data corresponding to onechirp as a single burst. This is possible because the data is allpresent in one continuous vertical block in the remote memory, which isfar faster than having to burst out the data in lots of individualbursts.

The method may in steps (c) and (e) store the data in the burst accessmemory in chirp order when scanning vertically down the memory block.

The method may transfer in steps (c) and (e) data in bursts having alength of at least 2 bytes up to N bytes where N is an integer valueless than the total number of antenna. The number of bytes that can betransferred each time depends on the available burst length versus thelength of each byte of data.

The method may comprise in steps (c) and (e) transferring the data as asequence of bursts to form the pattern of data in the remote burstaccess memory, with each burst containing the data for at least onerespective pair of range bins of the range bin set, with the data forone range bin being written into a left part of the column in the gridand for the second range bin being written into a right part of thecolumn.

The sequence used in steps (c) and (e) may transfer a first single burstcorresponding to range bins 0 and 1, followed by a subsequent singleburst corresponding to range bins 2 and 3, and so on until all the rangebins are transferred to the remote memory to form the pattern of storeddata.

Thus, reading horizontally across the row for each entry in the columnof data there will be the values for two range bins, one after theother.

To maximise speed of data transfer, the step (b) may comprise writingthe range bin values generated by the Fourier Transform into the fastlocal memory with each pair of range bins of the range bin set saved asa single data line, with the values for the first data bin in the lefthalf and the values of the second data bin in the right half.

If more than two range bins will fit in a burst the speed can beincreased by transferring three or more range bins at a time in eachburst in step (c).

The method may be used for cycles comprising more than two chirps simplyby repeating steps (a) and (b) as many times as there are chirp and thenrepeating step (c) for each chirp with the appropriate vertical offsetof the grid. It may be applied to a total of 512 chirps in each cyclefor example.

Steps (c) and (e) may each comprise transferring the data into a gridwhereby all of the data is held in a single column of width equal to theburst length. This column may store the range bin values for all of thechirps in a cycle in a single column. The column may therefore by two ormore bytes in width.

Where there are R range data bins, the data may be arranged in a patternin the remote memory after the data for a cycle of chirps has beentransferred so that all of the even range bin data is in the left handside of a burst-sized data line in the remote block of data and all ofthe odd range bin data is in the remote block of data stored in theright hand side of the burst sized data line.

To achieve this, in step (c) data may be stored in the remote memory ina pattern whereby the is a large gap left between subsequent singleburst lines that is equal to C−1 rows, ensuring that all of thefollowing repeats of step (f) will interleave into the gaps withoutoverwriting any of the previously transferred data from step (c) or step(f).

In a preferred arrangement, after all the data has been transferred intothe remote memory it may form a block of data which has no blank rows,and in which scanning down a column of the block all of the data valuesfor the N antenna for a given range bin are stored sequentially.

The block of data may be stored in a single column. This may in somecases allow the data to be read back in longer single bursts which ispossible with some remote burst access memory types for even moreefficiency.

The steps (f) and (g) may be performed with each cycle only once all ofthe data bin values for all antenna and all chirps have been transferredto the remote memory.

In a preferred arrangement, the method may be applied to a radarapparatus where there are N=16 antennas in the antenna array, which canbe identified as A0 . . . A15. There may be D=1024 real-valued datasamples in each chirp for each antenna with each data sample numbered D0. . . D1023 corresponding to a different frequency in the chirp.Alternatively the method may generate D/2 complex-valued data samples.

The first FFT performed in step (b) may generate R complex-valued rangebins for each chirp, where R is by definition D/2. This will result in256 data lines in the remote block of data for each set of range bindata with the odd ranges on the right of each data line and the even onthe left.

The first Fourier Transform step may comprise a Fast Fourier Transformof the type described in the text book by Cooley, James W., and John W.Tukey, 1965, “An algorithm for the machine calculation of complexFourier series,” Math. Comput. 19: 297-301.

Similarly, the second Fourier Transform step may comprise a Fast FourierTransform of the type described in that text.

The method may be repeated for a set of 512 chirps for each cycle.

The method may of course be repeated for a series of cycles duringoperation of the radar apparatus.

According to a second aspect the invention provide a frequency modulatedcontinuous wave (FMCW) radar apparatus comprising: an antenna array of Nantennas, a processing unit which receives data captured from theantenna array and includes an area of fast local storage memory and alarger area of remote burst access memory, and a set of program or logicinstructions stored in an area of memory that in use are executed by theprocessing unit wherein the method of the first aspect of the inventionis carried out.

The antenna array may comprise a set of N antennas that receivereflected analogue signals that are fed into an analogue to digitalconvertor that converts the analogue signals to digital signals.

The apparatus may also include a transmitter array of N antennas thattransmit a radar frequency signal away from the apparatus, the frequencybeing in the range that can be detected by the N antennas.

The apparatus processing unit may generate drive signals for thetransmitter array or may configure a remote radar processing chip togenerate the required radar signals.

According to a third aspect the invention provides a set of programinstructions held in a memory of a processing unit of a radar apparatuswhich when carried out by the processing unit cause the radar apparatusto perform the method of the first aspect of the invention.

Other advantages of this invention will become apparent to those skilledin the art from the following detailed description of the preferredembodiments, when read in light of the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block schematic of a radar apparatus in accordance with thepresent invention;

FIG. 2 is representation of the arrangement of data in the local storagememory for one chirp N=n showing how each data line stores the rangedata bin value for pairs of range data bins,

FIG. 3 shows a sequence in time by which a pattern of data istransferred to the remote memory one burst at a time to build up a blockof remote data;

FIG. 4 shows the final block of data stored in the remote memory;

FIG. 5 shows the source of the transfer of a first vertical strip ofdata from the remote memory back to the local storage memory for asecond stage of FFT processing;

FIG. 6 shows the source of the transfer of a second vertical strip ofdata from the remote memory back to the local storage memory for thesecond stage of FFT processing; and

FIGS. 7 and 8 show the destination (in the local storage memory) resultsof FIG. 5 and FIG. 6; and

FIG. 9 shows the complete set of method steps carried out by theapparatus of FIG. 1 when processing one cycle of radar data.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows an exemplary FMCW radar apparatus in accordance with thepresent invention. The apparatus comprises a transmitter antenna array10 of N antennas, and a receiver antenna array 20 of N antennas. In thisexample there are 16 antennas, A0 to A15. The apparatus also includes aprocessing unit which transmits high frequency analogue signals to thetransmit antenna array in the form of chirps and receives digitised datacaptured from the receiver antenna array. Between the processor of theprocessing unit and the transmit antenna is a VCO 30, and between thereceive antenna and the processor is a RX mixer. The function of the VCOand mixer will be clear to the person skilled in the art.

The processing unit may include appropriate digital to analogueconverter circuitry and analogue to digital converter circuitry as shownalthough more commonly the output of the radar antenna array 20 willalready be in a digitised format. The A/D circuitry converts thereceived data from the mixer into a stream of data values. Theprocessing unit includes a processor chip and an area of fast on-chiplocal storage memory 50. The processing chip 40 is encoded with a set ofprogrammable logic instructions. The apparatus also includes an area ofremote burst access memory 60. This is a memory that is slower to accessthan the local memory but is optimised for access in bursts, e.g. dataof multiple byte length.

The skilled person will appreciate that the arrangement of thefunctional blocks shown in FIG. 1 is not intended to be limiting to thescope of the invention. The VCO and mixer could be implemented as partof the processing unit, and the A/D converter and D/A converter could beimplemented outside of the processing unit.

FIG. 8 shows the steps carried out by the embodiment of a radarapparatus shown in FIG. 1.

In operation, the apparatus transmits a chirp of frequencies from thetransmit antenna array and any echo signals that are reflected onto thereceiver antenna array generate a corresponding set of data samples. Inthe described embodiment each chirp produces 1024 data points for eachof the 16 antennas, so that in total there are 1024*16 data pointsgenerated for each chirp. The radar apparatus transmits multiple chirpsfor a single complete processing cycle, and in this embodiment acomplete cycle is made up from 512 sequentially emitted chirps, C0 toC511. The antenna may be uniquely identified by a sequence of numbersfrom A0 to A15, and may be arranged spatially in this order in theantenna array.

Each data point for an antenna will correspond to a single voltagesample captured by the ADC and will have a value that indicates theamplitude of an echo signal detected by the antenna at the associatedmoment in time.

The combination of the number of samples in each chirp, the high numberof chirps in each cycle and the number of antennas means there is a lotof data to process—of the order of 16 MB per radar cycle.

For each chirp, an FFT of the data is taken to produce a set of rangebin results for each antenna. Because there are 16 antennas in thisexample then for each chirp there will 16 sets of range bin dataproduced. Each range bin set in this example consists of B individualrange bins, where B is equal to 512, so that each range bin can belabelled uniquely as R0 to R511. Of course this is not intended to belimiting, as indeed the number of antenna in the array or number of datasamples for each chirp is not intended to be limiting.

As will be explained, the apparatus takes an FFT for one chirp but doesnot need to wait for all the chirps to be processed before writing outsome of the resulting range bin data to the remote memory. Each FFTcreates a complete set of range bins R0-511.

In fact, as explained in the following paragraph in this describedembodiment the data is written out each time a pair of range bins in therange bin set of the chirp have been calculated for every antenna. Thiscorresponds to only 32 bins of data in total needing to be calculated bythe FFT between each data transfer, corresponding to two set of 16 rangebin values for each range bin, each value corresponding to one antenna.

In a first FFT processing stage, prior to writing out any data to theremote burst access memory, the data for the first chirp starts to beprocessed within the processing unit. The FFT generates for the firstchirp all the range bin values R0-R511 for each of the 16 antenna.Taking advantage of the random access nature of the fast local storagememory the data is written into the local storage memory in a patternwhich is beneficial for fast transfer of the data to the remote burstaccess memory. Specifically, the data is saved in the fast local storagememory with the values for each of the antennas range bin 0, then eachof the antennas for range bin 1, etc.

Each set of 32 values (2 range bins, 16 antennas) is in a contiguousdata line. In the context of this description the term data line couldalso be interpreted as a ‘data burst’ i.e., the smallest efficient blockof data which the remote burst access memory works with. This is shownin FIG. 2 for one chirp n where n is any integer value between 0 and thetotal number of chirps in a cycle.

Once the chirp has been processed and stored in the local storagememory, each line is then transferred across to the remote burst accessmemory as a single burst of data. This is possible because the length ofthe data line is the same as the minimum length of a single burst. Bytransferred we mean that the data in the local storage memory is writtenout to the remote burst access memory; it can remain also in the localstorage memory until it is subsequently overwritten as it is no longerrequired for processing.

After the first data line has been transferred, each data line istransferred in sequence. This is transferred across to the remotememory. Importantly the second row is stored in the burst access memoryat a position offset from the first row of data by a number C−1 rows,i.e. if the first data line is written into row 0 this is written intorow 512. The subsequent bursts are also offset similarly.

This is repeated for all B/2 data lines needed to store the data makingup the full 512 sets of range bin data for the first chirp.

The sequence of 512 individual data transfers for all of the data binsgenerated from the first chirp forms a pattern of data in the remotememory that is shown in FIG. 3(a).

The next chirp is then processed in exactly the same way and transferredone data line at a time to the remote memory. However, the start rowposition for writing data to the remote memory in the transfer is offsetby one row to prevent this new data overwriting the data transferred forthe first row. The resulting data stored in the remote memory is shownin FIG. 3 (b).

This is repeated for each of the remaining 510 chirps, each time theoffset being increased by one row. At the end a block of data will beformed in the remote burst access memory as shown in the drawings. Itcan be seen that the horizontal dimension of a data line in the remotedata block is Antenna 0 to Antenna 15, twice . . . , once for even rangebins and once for odd range bins. The vertical dimension has the datafor range bins 0 and 1 stored in the first row and the subsequent rowsand the data for range bin 2 and 3 offset from row 1 by 512 rows, forrange bin 4 and 5 offset from row 1 by 2×512 rows and so on. At the endof the processing of the final chirp in the cycle there are no gaps inthe block of data in the remote burst access memory. All the datarelating to each pair of range bins is together in the remote burstaccess memory. This is shown in FIG. 3 (c) and also in FIG. 4.

Storing the data in the remote burst access memory in the patterndescribed above allows all the data for 2 Range bins to be easilybursted back into the fast local storage memory in a block of bursts orsingle long burst into a block of memory addresses in the local storagememory, allowing the a second stage set of FFTs to be done efficiently.

The data may be transferred back from the remote memory in the followingmanner.

Initially, a whole block of data 512 rows long corresponding to rangebins 0 and 1 is bursted (512 bursts) into the local storage memory. Thisdata is processed by a second stage FFT which works vertically on Rangebin 0 data on the left side of each data line. This data is thenprocessed by the FFT working vertically on Range bin 1 on the right sideof the data lines. This is shown in FIG. 5.

Further processing is then carried out on the so-called‘velocity-processed data’. This can take place in parallel with thereading in and FFT processing of the next pair of bins, but does nothave to.

After this has completed, then another block of data corresponding toRange bins 2 and 3 is transferred across in exactly the same manner asthe first block. This data is processed by a second stage ITT whichworks vertically on Range bin 2 data on the left side of each data line.This data is then processed by the FFT working vertically on Range bin 3on the right side of the data lines. This is shown in FIG. 6.

This is repeated for blocks corresponding to Range bins 4 and 5, and soon until the final range bins 510 and 511 are transferred across andprocessed to form velocity data.

The end results may then be processed some more and possibly alsowritten back out to an external storage. Again this can be done in along burst for the pair of results.

What is claimed is:
 1. A method of operating a radar apparatuscomprising an antenna array of antennas, a processing unit whichreceives data captured from the antenna array and includes an area oflocal storage memory and a larger area of remote burst access memory,the method comprising for a single cycle of the radar apparatuscomprising two or more chirps of transmitted radar frequency signal: (a)capturing a first chirp of data in the single cycle which generates datasamples from each of antennas and storing the data in the local storagememory, (b) processing the captured data using a Fourier Transform togenerate a set of range bin data, one for each antenna, where each setof range bin data comprises range bins, (c) transferring in a sequenceof bursts the range bin data for the first chirp from the local storagememory to a remote burst access memory where the range bin data isarranged in a grid pattern, the grid pattern comprising data filled rowscontaining two or more unique range bins of data for the first chirpheld in a continuous strip of the remote burst access memory, the datafilled rows being separated vertically from adjacent data filled rows bymultiple rows which do not contain any bursts of range data associatedwith the first chirp, (d) repeating the steps (a) and (b) for eachsubsequent chirp of range bin data in the cycle, (e) repeating step (c)after the range bin data for each subsequent chirp has been stored inthe local storage memory so as to transfer in a sequence of bursts therange bin data for each subsequent chirp of data from the local storagememory to the remote burst access memory where the data is arranged inthe same grid pattern used for step (c) but offset vertically by one ormore rows to fit within the rows in a column that have not been writtenwith range bin data for any previously processed chirp in the cycle, (f)transferring from the remote burst access memory into the local storagememory, in one or more bursts, at least one continuous vertical block ofrange bin data from the remote block that has a length equal to thenumber of different range bins, (g) processing the range bin datatransferred into the local storage memory using a Fourier Transform togenerate a set of velocity data comprising a set of velocity bins whereeach velocity bin is generated from the values of the correspondingrange bin for every antenna of the array, and (h) repeating steps (f)and (g) until all of the range bin data in the remote burst accessmemory block of data has been processed by the second FFT.
 2. The methodof claim 1 comprising in steps (c) and (e) store the range bin data inthe burst access memory in chirp order when scanning vertically down thememory block whereby for each subsequent chirp the grid pattern isoffset vertically by one row.
 3. The method of claim 1 comprisingtransferring in steps (c) and (e) range bin data in bursts having alength of at least 2 bytes up to N bytes where N is an integer valueless than the total number of antenna.
 4. The method of claim 3comprising in steps (c) and (e) transferring the range bin data as asequence of bursts to form the grid pattern of data filled rows in theremote burst access memory, with each burst containing the range bindata for at least one respective pair of range bins of the range binset, with the data for one range bin being written into a left part ofthe column in the grid and for the second range bin being written into aright part of the column.
 5. The method of claim 1, in which steps (c)and (e) each comprise transferring the range bin data into a gridwhereby all of the range bin data is held in a single column having awidth equal to a burst length.
 6. The method of claim 5 where there arerange data bins and the method transfers the range data bins to theremote access memory arranged in a pattern after the range data bin fora cycle of chirps has been transferred so that all of the even range bindata is in the left hand side of a burst-sized data line in the remoteblock of range data bins and all of an odd range bin data is in theremote block of range data bin stored in a right hand side of the burstsized data line.
 7. The method of claim 1 in which the range bin datatransferred to the remote burst memory is stored in a pattern wherebythe number of blank rows left between subsequent single burst line isequal to C−1 rows, ensuring that all of the following repeats of step(f) will interleave into the gaps without overwriting any of thepreviously transferred range bin data from step (c) or step (f).
 8. Themethod according to claim 1 whereby after all the range bin data hasbeen transferred into the remote burst access memory the range bin dataforms a block of data which has no blank rows, and in which scanningdown a column of the block all of the data values for the antenna for agiven range bin are stored sequentially.
 9. A frequency modulatedcontinuous wave radar apparatus comprising: an antenna array ofantennas, a processing unit which receives data captured from theantenna array and includes an area of fast local storage memory and alarger area of remote burst access memory, and a set of program or logicinstructions stored in an area of memory that in use are executed by theprocessing unit according to the method of claim
 1. 10. The frequencymodulated continuous wave radar apparatus according to claim 9 in whichthe antenna array comprises a set of antennas that receive reflectedanalogue signals that are fed into an analogue to digital convertor thatconverts the analogue signals to digital signals.
 11. A set of programinstructions held in a memory of a microcontroller of a radar apparatuswhich when carried out by the microcontroller cause the apparatus toperform the method of claim 1.